Blanks for dental restoration parts are typically machined, in order to achieve an adaptation to the desired shaping. While precision work and adjustments have to be performed in the adaptation of the dental restoration part by the dentist, or generally by the dental technician, typically blanks produced in block form are brought into shape in advance, in order to restrict the adaptation work to a reasonable amount.
This applies to a particular extent to dental restoration parts and corresponding blanks made of ceramic. Ceramic materials—especially zirconium dioxide—are particularly hard, so that it is desirable to reduce the machining that has to be performed in the dental laboratory to a minimum.
On the other hand, ceramic blanks can be produced exceedingly well in block form. Therefore, based on the suitably selected raw material, a blank is pressed in block form and sintered in a sintering furnace.
With regard to the particular hardness of ceramics, such as for example zirconium-based ceramics, it has also already become known not to machine the fully sintered product, which is very hard, but a pre-sintered product, which already has sufficient stability for machining. As a result, the wear of the tools that are used for the machining, that is to say for example milling cutters or turning tools, can also be distinctly reduced.
For the machining, the blank must be received in a suitable way in the work holding fixture of the machining device. Often used for this purpose is a holding pin, the outer shape of which is formed suitably for the work holding fixture and is cemented in a bore in the blank. See for example U.S. Pat. Nos. 6,224,371 and 6,627,327. However, to this extent the anchoring of the blanks for the machining is extremely complicated and also susceptible to errors. In particular, it must be ensured that a predetermined position is ensured for the fixing between the pin, which is held in the work holding fixture, and the blank.
Furthermore, it has also already been proposed to configure a support with an adhesive area, on which the blank is adhesively attached. See for example U.S. Pat. Nos. 4,615,678, 7,214,435, and 7,255,562. This also allows in particular blanks of different sizes to be used with the same work holding fixture fixing pin. Typically, such an adhesive area is planar, in order to ensure a particularly good contact with a surface of the blank, which is initially in block form. As a result of this, the spatially fixed fixing of the blank is difficult, and it is typical in the case of such a configuration to resort to forming a differential dimension, which relates a side face of the blank to a side face of the insert pin, and using this as a basis for fixing the connection between the insert pin and the blank. This is indeed possible in principle and can also be automated by machine, which is necessary with regard to the numbers of items to be produced.
However, precisely in the case of different work holding fixtures, it is necessary to use different insert pins, which accordingly have different dimensions. However, the combination of such different insert pins, in a number corresponding to the work holding fixtures used, with different blanks leads to a multiplication of the possible combinations, so that fixing such a differential value would be significantly too complicated in practice and therefore this has not been widely adopted for understandable reasons.
It has also been proposed to provide a blank which is attached to a support plate mounted on a holder section that is received by a boring inside a shaft part of a holding device. See German Patent 197 33 161. In this design a clamping screw is used to fix the holder section into position. A groove extending around the outside of the holder section mantle receives at least part of the screw, which is smaller than or equal in size to the groove.